Adaptive approach to load shedding including pumped-storage units during underfrequency conditions
An adaptive approach is proposed to load shedding including the consideration of pumped-storage units during underfrequency conditions. Based on the idea of average or uniform frequency behaviour, a load-frequency control model is utilised in the scheme design. At this stage, Taiwan Power Company (Taipower) owns ten pumped-storage units that amount to about 13% of the total rating capacity. These units can be operated in generating mode during peak period, to reduce generation cost, or operated in pumping mode during off-peak period, to consume the surplus power. As the difference between the peak load and off-peak load of Taipower is considerable, pumped-storage units are playing a critical role in Taipower operations. Once disturbances take place in off-peak periods, pumped-storage units can be thus shed with a high priority. As they are useful in both restoring system frequency and decreasing the degree of service interruptions, these pumped-storage units have been included in the proposed load-shedding scheme design and tested through the utility data. From test results and comparisons with the existent utility shedding scheme, they have demonstrated the feasibility and practicality of the method for such applications.
